1. Field of the Invention
This invention relates to a support, specifically a fibrous support adapted to support an enzyme, a microorganism, or cells thereon in an immobilized state and used as contained in a reaction vessel, for example, and to a method for the production of the fibrous support thereof.
2. Prior Art Statement
In recent years, immobilized enzymes, i.e. enzymes immobilized on suitable carriers, have been finding utility in the continuous production of various organic acids and saccharides. The advantage of this utility in terms of quality of product, cost of production, and economy of energy consumption has been attracting keen attention.
The methods available for the immobilization of enzymes are broadly grouped under the gel-entrapping method, the cross-linking method, and the carrier binding method. The carrier binding method can be further subgrouped into the covalent bond method, the ionic bond method, and the physical adsorption method. The immobilized enzymes obtained by these methods are generally in the form of gel, granules, or film and are used as packed in reaction vessels such as columns. These methods are applied not only to enzymes but equally to microorganisms and cells.
In uses of this type, the total capacity for treatment per unit volume of support and the speed of treatment, i.e. the volume of a gas or a liquid (hereinafter referred to as "fluid") to be treated per unit time, are matters of concern. For the purpose of improving the speed of treatment, the granular immobilized enzymes of reduced size are currently in common use. The effect of this size reduction consists in increasing the area of contact per unit volume of support and decreasing the distance of diffusion of materials in fluid within particles.
The size reduction of granule, however, increases the resistance the bed of the support offers to the fluid being passed therethrough. There is a possibility that in extreme cases, the passage of the fluid under treatment will become very difficult to achieve.
The method for immobilizing enzymes on fibers has also been proposed in the art (Japanese Patent Publication Nos. Sho 55(1980)-47130, Sho 57(1982)-17083, and Sho 57(1982)-17087, etc.).
The support having an enzyme immobilized on fibers, as compared with the granular support, has an advantage that it permits secondary fabrication into yarns, cords, woven fabric, knitted fabric, non-woven fabric, felt, or mat and enjoys a high speed of treatment. The advantage is ascribable to the fact that the individual filaments which make up the support are slender columns and, therefore, have a large area of contact and a short distance of internal diffusion. And the fibrous support offers smaller resistance to a fluid compared to that of a granular support, because of the bulkiness characteristic of fibrous materials.
In connection with the fibrous support described above, the idea of efficiently attaining an enzymatic reaction by means of an enzyme effectively immobilized on fibers having an average diameter of less than 1 .mu.m has been disclosed to the art.
The fibrous support, however, generally has a disadvantage that it is liable to undergo compaction when it is continuously used for treating a fluid in motion at a high flow rate. This compaction is caused by the resistance offered by the fluid in motion and, in consequence of this compaction, the support itself gains in its own resistance offered to the fluid and further accelerates the progress of the compaction, starting a vicious cycle of increasing resistance and accelerating compaction. Once the compaction occurs in the support, it progresses rapidly even to the point where the treatment of the fluid will become substantially impracticable.
This phenomenon of compaction is liable to occur where the fibers have low bending rigidity, namely the component filaments are made of a soft substance and have a small diameter. The aforementioned fibers having an enzyme immobilized thereon are very thin and liable to be softened and, therefore, exhibit extremely low bending rigidity under water. When these fibers are used as a support without any modification, they are liable to undergo very serious compaction.